1. Field of the Invention
The present invention relates to filtered electrical connectors of the type utilizing planar monolithic filter arrays.
2. Description of Related Art
It is known to provide electrical filters in connectors for the purpose of protecting sensitive components from transient currents and voltages which develop in a transmission cable due to electromagnetic and radio frequency interference. Such transients are generally high frequency in nature, and therefore capacitive or tuned pi circuits are used to shunt the transients to ground without affecting the primary signal carried by the cable.
Conventional designs generally fall into one of two categories: The first category includes filter connectors in which monolithic capacitor blocks are used. The capacitor blocks generally consist of a planar block of dielectric material with interleaved ground and hot electrodes arranged to be electrically connected with pins inserted through holes in the blocks. Such blocks are convenient but are disadvantageous in that customizing of capacitances for individual pins is difficult, due to limitations of the single dielectric material used for the block and also the need for additional manufacturing steps and tooling. Moreover, if any one capacitor is defective, the unit must be replaced. When combined with ferrite blocks or tubes to form pi filters, problems arise in combining the two ceramics, ferrite and dielectric, and subsequent electroding is relatively difficult.
The second category of prior capacitive or pi filter designs involves utilizing discrete cylindrical capacitor or pi filters which are formed as filter sleeves for the pins and are grounded to the connector shell through a conductive ground plate which can be metal (normally plated) or a metalized dielectric ground plate. These designs are disadvantageous in that the filter sleeves are fragile and require relatively complicated grounding arrangements. In addition, the use of ceramic supporting blocks increases the risk of damage to the arrays.